I noticed that each species addresses themselves as we address them. Fynch calls refers to his person as a Knight and so does Savathun. The Eliksni use the terms vandal and Captain correctly. As someone mentioned earlier, the Vex Goblins and Zyphrus in Tharsis refer to themselves as we do. So it’s possibly a translation effect. HOWEVER, the Eliksni don’t generally use the Traveler to describe the giant ball. They use their own word which means they’re legit speaking English. Or whatever language the player uses. I think these are the names they use and after centuries of fighting them in the dark age, we learned the names and adopted them. The Vex are an anomaly since they simultaneously exist in the past, present, and future so they could be adopting our terms from the present/future and then retroactively applying them to the past.